CPEB is a component of the nuclear RNA processing machinery. (A) Symplekin was immunoprecipitated in the absence or presence of RNase A from ∼250 LMB-treated hand-isolated oocyte nuclei. A similar number was mock precipitated with nonspecific IgG. The precipitates were probed on Western blots for the proteins noted in the figure. Actin served as a negative control; 1% of the extract was also applied directly to the gel without immunoprecipitation. (B) Similar to panel A except that CPEB was immunoprecipitated from the nuclear extracts. (C) Oocytes were injected with mRNA encoding myc-tagged Gld2; following overnight culture, the nuclei were isolated and subjected to CPEB immunoprecipitation as in panel B and probed for the proteins noted in the figure. (D) Fractionation control from oocytes used in panels A–C and E; tubulin, a cytoplasmic protein, is entirely cytoplasmic, while CBP80, a nuclear protein, is entirely nuclear. (E) CPEB was immunoprecipitated from oocyte nuclei as before; the RNA was extracted from the precipitates and subjected to RT-PCR for the RNAs noted in the figure.
